Wedding Party

So the wedding is 14 months away, I'm starting to look at different options for the wedding party attire. We live in a different province so both of us are unable to go shopping with our parties. So I am trying to figure out a deadline for them. My fiance and I will probably go looking and dresses and suits for them to get an idea this summer so around the 1 year mark or a bit later. So I'm thinking of having them all have their attire by the 6, 5 or 4 month mark, which do you think is good for them to buy it before? and then they can have all their alterations done a month or so before the wedding.

My side of the wedding party is 90% on board with everything. My one bridesmaid is a little iffy but she's going through a lot right now so her attention is usually elsewhere. Although she is very good with deadlines so when I figure out the wedding party attire deadline then I know she will be good for that. However I have zero confidence in the groomsmen. For my girls they get to pick their own dress just with the guidelines I give them. For the groomsmen we were going to go with same colour obviously but a bit of a mix look so one with a vest, other with suspenders etc.. but I seriously have absolutely no confidence in any of them other than the best man to get this done. There is one in particular who's gf is way too controlling and I worry she will get in the way of this. My fiance hasn't thought I'd this but he knows how this one gf is. So I'm thinking my fiance and I pick the suits for each one, set it up to have them delivered directly to them individually and have them pay us. If they don't pay us then they don't get ordered and they can't be in the wedding party, is this fair? I mean they will have about 6-8 months to give us the money before the deadline.

So do you think the deadline I picked is reasonable? Do you think is picking for the groomsmen then sending them after they pay us is reasonable?